Liquid-operated classifier



April 3, 1945- JD. B. PHIPPS l 2,373,051

LIQUID-OPERATED CLASS IFIER Filed June 21, 1944 1o sheets-sheet 2 April .3, 1945- J'. D. "B. Pl-HFF'S .2,373,051

' LIQUID-OPERATED `CLASSIFIER Filed June 21, 1944 10 Sheets-Sheet 5- v April 3, 1945.

J. D. B. yivf-n PFs d 2,373,051

LIQUID-OBERATED CLASSIFIER Filed June 21, 1944 1o sheets-sheet 5 April 3, 1945.

Filed June 21, 1944 l0 Sheets-Sheet 6 l0 Sheets-Sheet 7 Filed June 21. 1944 pril 3, 194s. J D B, PH|PP I 2,373,051

LIQUID-OPERATED CLASSIFIER,I

. Filed June 21, 1944 1o sheets-shed 8 gay v April 3, 1945. J. D. PHIPPS 2,373,051

' vLIQUID-01: ERATED GLASS IFIER Filed June 2l. 1944 lO Sheets-Sheet 9 ffy/2 OOO OOO

April 3, 1945. 1 D Q pHlppS 2,373,051

LlQUID-OPERATED CLASSIFIER Filed June 21, 1944 v 1o Sheets-sheet 1o Patented Apri 3, tt@

buiten Sintes my LIQUID-OPERATED CLASSMIER r John Degory Baron Fhipps, London, England Application `lune 2li, 1944, Serial No. llLilfi lin Great Britain .Enne lll, 1943 n creams. (ci. ccaicm The invention relates to classiers ci the hln- -dered settling type. In my British Patent No. 553,604 I describe a classierof this type in which a sand pump for the removal of the coarse race tion was coupled direct to the bottom outlet and the clean water inlet was above the outlet, the upward current for classifying being produced above the clean water inlet. A body termed a floating cone was adapted to float submerged at a varying level in the upward current of liquid and the classifier casing was tapered to increase in width upwards and vary the now cross-section according to the height oi the floating cone.

lt is an object of the present invention to make a classier of thekin'd referred to suitable for material of -varying average particle size without changing the size at which split takes place.

It is a further object to provide means for varying the' physical composition of the coarse iracf Vfloating body, referred to as a compensating float or cone, cooperating with the floating cone to provide a second classifying column. For attaining the second object a second sand pump has its suction terminating in vthe column of liquid fiowing down with a swirling motion between the clean water inlet and the outlet to the rst pump, the position of the/suction end being adjustable to varying disances from the outside wall.

Further features of the invention will be apparent from the description now to be given of two forms of construction for washing sand and gravel illustrated in the accompanying drawings, in which part of the classifier alone without the overflow launder,

Figure l is a corresponding view ci the lower part.

Figure 11 is a sectional elevation of the float# ing cone,

Figure 12 is a sectional elevation of the compensating cone,

Figure 13 is an elevation and Figure 14 a plan of the feed inlet, and

Figure is an elevation and Figure 16 a plan of the overload device.

Referring to Figures l and 2, the body of the l with cylindrical upper part and is hereinafter referred to as the static cone. An annular overow trough 2 surrounds the top and discharges the waste water with the slimes into a pipe il. 'lhe feed is delivered by a helical launder or pipe d so as to cause a swirl for a purpose to be mentioned later. A conical sand chamber l -is mounted below the static cone l with an intervening spiral chamber or volute t, to which clean water can be admitted at 9 for washing the sand. An outlet pipe ll close to the apex or bottom of the sand chamber 'l leads to a sandpump l2 show n in conventional form.

Inside the static cone i a body id is placed so as to be completely submerged during normal Figure 1 is an elevation partly in section of one form of classier, Y

Figure 2 is a sectional plan on the line II-II of Figure 1, Y

Figure 3 is a front elevation of another form of classifier with its ancillary apparatus,

Figure 4 is a side elevation of the sama' Figure 5 is a sectional elevation on the line if-V of Figure 4, Figure 6 is a sectional planv taken on the irst iioor of lthe structure,

Figure 7 is va sectional plan taken on the second door,

Figure 8 is a top plan, Y Figure 9 is a sectional elevation of the upper operation. The shape of this body in the form shown in the drawings is a cylinder with a cone on each end face. I prefer to call this body the floating cone. The :licating cone it is xed in a water-tight manner to the lower end of a tube 3d extending well above the liquid level in the static cone and provided with two internal bearing bushes 35, 35. A smallervertical tube 36 is nxed by a channel iron 3l to the static cone i and acts as journal for the bearings A collar 38 at the lower end of the tube 36 serves as a stop to limit the downward movement of the tube it and vcone ld, and an upper collar 39 similarlylimits the upward movement.

Attached to the oating cone i8 lis a compensating float dll. 'This is an annular hollow body in the shape of a cylinder with a rustuzn of a cone on each end face. The compensating float tu is bolted at an adjustable height to a cylinder1 dl fixed by iou'r Vanes d2, di to the tube 3d. The

-vanes d2 are vertical, so that the .swirl of the staticv cone as will be further explained later.

. falling material.

AFigure 1 shows the ,oating cone and compensating float in their highest position. The chain dotted llines on the right hand side represent the portions of these elements defining4 the ow channels with the static cone when they are in their lowest position.

'I'he volute 8 has an inner wall 43 with eight equal inlet ports 44, 44 to give an even peripheral distribution of the incoming clean water. The swirl from the volute 8 should, of course, be in the same direction as that from the helical launder 4.

The static cone l is provided with a window 45 by which the operator can observe the be.- haviour of the material being treated. The top edge of the static cone I forms aweir for discharge into the overilow trough 2. This edge is made adjustable in height by means of an external ring 46 bolted to it. An adjustment of 2 inches each way from the mid position will probably be found sumclent.

The oating cone l is made hollow with access to the interior by means of the tube 36, so that the cone can have a suitable quantity of concrete or sand placed in it to adjust the weight nearly to the correct value. The addition of such material helps to keep the centre of gravity of the structure low. Alternatively the oating cone could be made of concrete. The tube 34 carries near the top a weight box 41 into which weights can be put for the iinal adjustment of weight of the structure I8, 34 and 40 to suit the required conditions.

The principal function of the iloating cone is y to regulate the velocity of the upward current ly called -100 mesh grains) so also those falling would be limited to those larger than 100v mesh (usually called +100 mesh grains) Underthese conditions an exact split at 100 mesh would be obtained provided that their average falling velocities remained constant.

Suppose now that due to a change vin the compositionof the sand the average falling velocity increased to such an extent that the upward current corresponded to'that of a grain of 80 mesh falling in a stationary mixture of the same speciiic gravity, no -80 mesh grains would fall.

This would cause an accumulation of grains between 80 and 100 mesh (usually called 80 +100 mesh?) which could go neither up nor down.

These could only accumulate under the compensating float 40 thereby increasing the speciilc gravity of the mixture there and causing the float to rise, and at the same time to lift iioat I8 to such an extent that the upward current at the constriction would be reduced until grains down to 100 meshcould fall. Equilibrium would be re-established, and the split would take place once more at 100 mesh. As the static cone I is stationary, the compensating iioat 40 in rising has increased the gap between itself and the inner surface of the static cone immediately under between it and the static cone to an approxie mately constant value whatever the rate of feed. By floating on the rising current'the cone will rise with any increase of current until equilibrium is established between its apparent weight and the dynamic effect of the upward current. Similarly a decrease in the upward current will cause the cone to fall. The flow velocity thus remains the same and the split is eiectedat the same particle A the top of the static cone I is made of such a.

diameter that the vertical velocity of the dirty water rising to the overflow is equal to that of a sand grain 100 mesh in size falling in a stationary mixture which is of. equal specific gravity to that which is overowing. Bygthis means the size of grains overflowing should be limited to those. smaller than 100 mesh. The weights in the weight box 4l are then adjusted.` so that the velocity of the watervrising in the constriction between the floating cone Is and the static cone l is equal to that of a sand 'grain of 100 mesh inv size falling in a stationary mixture which is of equal speciilc gravity to that in the constriction.

vThere is, of course. aconsiderable diierence between these two specific gravitiesl and velocities, but just as the size of grains overflowing would be limited to those smaller than 100 mesh (usualit. This would reduce the velocity of the rising current in the gap and, until a corresponding increase in the specific gravity of the mixture there takes place, grains between 100 and 120 mesh would be unable'to rise. Inbeing unable to .rise they would themselves create this corresponding increase in specific gravity which would cause an unwanted rise in the compensating float.

It is to correct this tendency that the upper part of the compensating float is made to emerge from the water. The loss of buoyancy resulting lis made to balance vout the effect of this unwanted secondary accumulation of grains. Looked at in another way, the action of the compensating float with access ladders 49 to the various floors.

corresponds to the automatic removal of weights from the weight box 41 when the average falling velocity increases.

Referring now to Figures 3 to 16, the static cone I is of the same general shape as before and is shown in Figures 4 and 5 mounted on a three-storey frame 48 of constructionalv ironwork The principal differences from the classifier previously described are that the compensating float is movable independently of the floating cone and that a second pump is provided to abstract some of the clean sand on its way to the said cone.

The sand to be cleaned is raised by a said pump (not shown) through a pipe 50 into a boiling. box 5I. From here it flows by a chute 52 into a secondary tank 53, which discharges intoa static tank 54 of inverted pyramidal form. The

" material enters the static tank 544 through a From the apex (bottom) pf the static tank apipe 5l leads to the feed inlet, of which details are shown in Figures 13 and 14. fThe feed inlet is suspended on thechannel iron 31 and comprises a cylindrical box 58 with inner cylinder 59 to form an annular water space of rectangular section. The top platenil is made in halves and is carried down well below the bearing bus to keep the bearing `free from sandI as faras 45 viewed in plan and with a downward slope to. produce a swirlin'the water space.

Four square holes 6|, 6| are equally spaced in the bottom plate, and a loose plate 32 with cor- 5 responding holes overlies the bottom plate. The loose plate 62 can be adjusted in positionto vary the effective aperture of the holes 3l, 6l. In theB outer cylinder 58 there are also four rectangular ports 63, 63 staggered in relation to the holes 10 6i, tl.- A diverting plate 34 is fitted over each port 53 to assist in maintaining the swirl of the material issuing therefrom. The tops of the ports |33 are below the water level determined by the annular overow 2. The `combination of 15 adjustable holes and ports makes it possibleto regulate the centrifugal velocity of the suspension entering the static' cone to suit the conditions.

The channel iron 31 as before carries a xed 20 vertical tube 33 to serve as' a bearing'i'or the supports ofthe oats. The tube -36' is polished on the outside and carries a ring for supporting the iloats when the static cone is empty. The

fioatingcone I8 lhas a tubular shaft 34 with an o internal ring 66 near the bottom to serve as a bearing bush and an internal ring 61 at the top, which serves as a bearing bush and also engages the ring when the static cone is empty. Up-

ward movement of the floating cone is limited by 30 The tube l!! has an internal bearing bush 1l of rubber or-lignum vitae and an internal ring 12 at the top. lThe vertical movement of the compensating oat 40 in relation to the ioating cone it is limited in the upward direction by contact 40 of the ring 12 with the ring 63 and in the downward direction by contact of the;1ower en f the bearing 1l 'with the ring 68. The -tub possible. l

'The top edge of the static cone i is` provided with 4a ringl, of adjustable height to form a weir plate. The parts are so dimensioned that in every operating position of the weir plate 46 50 and the compensating float I3) the water level in the static cone -I-`-"is on the cylindrical part of the oai,- lli. In respect the present con` struction diiers from that ol'V Figure 1, where the water level was on the upper conicalsurface 5 5 of the oat 40. I

Clean water for washing the sand is supplied from a--tank 13 on the top ofthe framework, passing down by a pipe 14 through an adjusting valve 15 to the inlet 9'of the clean water volute 6o 3. The form of the volute is as shown in Figure 2. A certain proportion of the water fed in at the volute 8 passes upwards "through the annular constriction between the static cone l and the iioating cone i8 and classifies the materiaiin a |65 sorting column thereabove on the hindered settling principle. The floating cone in the present `form has its middle part carried with the apex downwards, so that the specific gravityof the suspension` in' the sorting column may exert vsofine 70 l .The height'to 'which clear water will risein these glasses above the level in the static cone indicates Athe speciiic gravities of1 the mixture at the differ-A eiect on the cone. Vanes 30 on the under side of the floating cone help to keep the cone in slow rotation due to the swirl. The sand cone 1 is attached 'to the volute 3 v l andv terminates in a T piece 11. The sand pump I2, driven by a motor 13, is connected to one branch of the T piece 11 through a main faulty operation can be' cleared by opening the valve I1 and closing. the valve 15, allowing the pump il. to remove the said.

A bent suctipn pipe 13 passes through the conical wall of the sand chamber 1 by a screwed socket in which it can turn freely. A shaft 8i in line with the part of the pipe 19 passing through the chamber wall isr xed to bend and passes through the wall of the cylindrical portion 13 by a gland 32. A hand wheel 33 is xed to the shaft on the outside. In-the position shown in gure l0 the inner end of the pipe 19 is central and vertical. By means of the hand wheel 33 the pipe 19 can be moved to bring its open end near the wall of the sand cone vl to any intermediate position between that and the central position shown. One spoke of the hand wheel has an arrow cast on it to act as an index. This is the spoke in line with theupper end of the pipe 19 when viewed along the axis of the shaft 8l.

The outer end of the pipe 19"is connected through a valve 8d to a vsecond sandpump 85 driven by a motor 86. The pump 83 abstracts some of the sand falling in the sand cone 1. The swirl in the sand cone gives rise to a radial grading of the falling sand particles. In the position of Figure 10 the abstracted particles are 'those at the centre `and in the other. extreme position those near the outside, while in intermediate positions particles of intermediate ranges are abstracte'd` @The yquantity abstracted can be adjusted b. means of the valvefli, but adjustment should not be made during operation.

The classifier may have to operate with varying feed and will take care Ofyariations up to full load. In case the feed should increase still further, it is desirable to have van overload dc` vice.

the forked end of a lever 88 pivoted at 89on a bracket attached to the channel iron 31. mally the ring is about an inch below a stop ring 30 attached to the channel iron 31.

ring 81 at the full load position.

The outer end of tlie lever 88 is connected by u a tie rod 9i to a lever 92 carrying a cut off gate.l

Jon the extent to which thegate 93 `rises and ac.

cordingly on the riseof the floating cone i8.

For the purpose of observing the operation the static cone I is provided with two 4inspection windows 95, 95 above and below Ithe clean .water volute 8. In addition three pipel sockets 9 6, 96

are fitted in the positions shown to receive ilex-l ible rubberconnections for `vertical gauge glasses;

ent points.

in the present ca se by' a cylindrical portion`16 iiik `The Weightoi? theiieating cone I8 can be ad- For this purpose a ring 31 is mounted toslide on the vertical tube 313. It is supported by Nor- When on account of an increase 'in load the floating cone i8 rises, its top rings 61 and 39 just reach the sand fed in.

nowing upwards but with no sand fed Justed by pouring sand or water down the supporting tube 34. A plug 91 is provided at the bottom of the iloating cone, by which the water or sand can be removed, if the weight is to be reduced. 'I'he compensating oat 40 can have its weight adjusted by adding water through a plug hole 98 or removing itthrough plug holes 89, 09. A central Weight box would obstruct the inlet box, but pegs |00, are attachedto the compensating float, upon which weights can be hung.

In operation the speeds of the two pumps and their valve settings should remain constant at their adjusted values. Before any sand is fed in a balance should be struck between the quantity of clean water flowing in by the volute'Il and that being removed by the pumps I2 and 05. The opening of the valve 84 and the position of the suction bend are adjusted in accordance with the known physical analysis of the-sand to be treated and the change ot composition required..

When both pumps are running, the static cone I should remain brim full or overilow very slightly.

. Then, when sand and dirty water are fed in,'the

sand itself causes its own upward current by displacement rin direct proportion to the quantity'of The feed of dirty sand and water should be'kept approximates' constant in' unr. however, the sand content may vary.v This is effected automaticallyby the static tank El, reed pipes 51 and valve IOI. f

yend of the bearing bush 1I. From that point to full load the two cones move together as one structure l l 'There is a diierence in operation between the two sorting columns, as will now be explained, but the periodic accumulation ofgrains near the split size occurs in both. In the lower sorting column between the floating cone Il and the lower Dart of the static cone I the conditions are thoseof true hindered settling, since the quantity of sand falling inthe whole output of cleaned sand and the-rising current of water is equivalent in bulkto the sand falling, as explained above.

Thef'rising current in the upper sorting column between-the compensating cone 4I and the upperv part oi' the static cone I is made up of the water rising from the lower' sorting column and the water supplied with the feed of dirty sand. The latter lquantity is considerably larger thanv the former; it may be four times as much at full load and an 'even greater proportionjat lower loads. The solids in this sorting column are only the silt rising to the .overflow and a few Isand grains near `the split size, a much smaller quantity han in the'lower sorting column. 'Ihe condit dus are therefore practically those of Afree, set

The respective ow velocities should be regu-V' lated in acordance with these diiiering settling The floating cone I8 and the compensating iloat or cone` each have a lower conical suri'ace L cooperating with the interior conical sm'i'ace oi' the static cone I to form a lower and an upper sorting column respectively. Figure 9 shows both cones I8 and 40 at their highest positions on the left hand side and at their lowest positions on the right hand side. In the case of both sorting columns the cross-section is not the same at all levels, and in most positions there is a maximum cross-section somewhere in, the column with a gradual reduction both upwards and downwards.

'I'his feature was originally considered tov be adrawback which should be avoided, -but the present invention makes use of it. As classication proceeds there is a gradual accumulation of grains of asize very near the split, which cannot go up or down, because the ilow velocity is a.`

maximum at the lower part of the'sorting column between the oating cone I0 and the static` cone I and diminishes in the upward direction. This laccumulation increases the eiective speciilc gravity of the sand and water mixture and exertsincreased pressureon the middllevconical part of the iloating cone I0, causing it'to rise. The reduced now velocity due to the increased' cross-section permits a considerable proportion of the grains so accumulated to pass down to the sand chamber 1. The reduced effective speciiic gravity in thesor'ting column then allows the floating cone I8 to fall a little. and the proceisscommences again. A rather similar effect takes A place in the upper sorting column between the compensating float 40 and the static conc I.

At no load. that is with a minimum oi'I water in, both cones I0 and 40 will be at their lowest position as shown on the right hand side of Figure 9. As the i'eed of sand increases from zero, both cones -rise independently or each other to equilibrium positions' dependent on the rate oi' ieed. At some point dependent on the slit or mud contento! the dirty sand the iloatlng cone I0 overtakes the the tube I4 come; into contact with thelower conditions, that is, the vertical 'velocity of ow -one to achieve split at the same particle size.`

The lower conical face of the compensating iioat 40 should be of such a shape that, when the float is half way between its extreme upper and lower positions, the vertical .component of the velocity of now between it and the -upper conical part of vthe static cone I is equal to the vertical velocity of the waterin the space above bounded by the cylindrical parts of ythefloat ll and the static cone v It may in some cases be desirable tohave the compensating float 40 rigidly attached to the oating cone I0 as in 'the case otFlgure 1. For this purpose set screws may be passed through the ring I into the tube Il..

Theclassiilei' of Figures 1 andV 2 can be mountl ed with its ancillary apparatus on a structure like 40 for convenientI access and operation.

WhatIclaimis: l 'r 1. Aclassiiier of the hindered settling type comprising a static cone with its apex downwards and-its top open for the overilowoithe ner fraction, a feed inlet at the top for water containing in suspension the material to be classied, a clean water inlet at the-lowerxend oi' the static cone, a. body located tto float submerged at avariable level in the lower part oi' the-static cone and to deilne between itselil and the static cone a hindered settling column of variable crocssection, a second body located-toiloat partly submerged at a variable levelin the upper Dirt of the4 static cone and to define between itself and the static cone a classifying column of variable crosssection,'a sand chamber below the cleanf waterinlet to collect the coarservi'ractitm,4 and f a pump connected to the sand chamber to remove water with the coarser traction in suspension.

2. A classiiier oi' the hindered comprisingl a static cone with its and its top'open tor the ,overowof the ner fraction, a feed inlet at the top for water con-y -compensating cone l0, and the outer ring I8 on l teining'in Suspension the material to be classied, a clean water inlet at the lower end o! the static cone, a body located to iioat submerged at semina type l apex downwards a variable level in the lower part o f the static cone and to define betweenitself and the static cone a hindered settling column of variable cross section, a second body attachedto the aforesaid body to move in unison therewith and located to float partly submerged at a variable level in the upper part of the static cone and to define between itself and the static cone a classifying col'- umn of 4variable cross-section, a sand chamber at a variable level in the lower part of the static l cone and to define between itself and the static cone a hindered settling column of variable crossco'arscr fraction in suspension.

6. A classifier as defined in claim 5v in which the 4 second floating body is xed to the second tubular shaft by means permitting adjustment of the relative heights of the two floating bodies.

'7. A classifier of the hindered settling type comprising a static cone with its apex downwards i and its top open for thevoverflow of the liner frac- 1 tion, a feed inlet at the top for water containing section, a second body located in the upper part ofthe static cone to float partly submerged at a variable level independent at least in part of the floating level of the first body and to define between itself and the static cone l a classifying column of variable cross-section, a sand chamber below the clean water inlet to collect the coarser fraction, and a pump connected to the sand in suspension the material to be classified, a clean water inlet at the lower end of the static cone, a tubular shaft xed in relation to the static cone and projecting vertically'downwards atthe centre thereof, a second tubular shaft embracing the first and movable vertically in relation thereto, a body attached to the lower end of the secc-nd tubular shaft to float submerged in the lower part of the static cone and to define between itself and the static cone a hindered settling column of'variable cross-section, cooperating abutments on the outside of the first tubular shaft and the .inside cf the second to limit the vertical movement of the second tubular shaft and the floating body, a third tubular shaft embracing the second and movable vertically in relation thereto, a second body fixed chamber to remove water with the coarser fracl tion in suspension.

4. A classifier of the lhindered settling type comprising a static conc with its apex downwards and its top open for the overflow of the finer fraction, a feed inlet at the top for water containing in suspension the material to be classified, a clean water inlet at the lower end of the static cone, a body located to float submerged at a variable level in the lower part of the static cone and to dene between itself and the static cone a hindered settling column of variable crosssection, a second body of annular form located to floatr partly submerged at a variable level in the upper part of the static `cone and to denne between itself and the static cone a classifying column of variable cross-section, the feed inlet being arranged to discharge the material inside the said second body, a sand chamber below the clean water inlet to collect the coarser fraction, and a pump connected to the sand chamber) to removef'water with the coarser fraction in suspension.l f K 5. A classifier of the hindered settling type comprising a static cone with its apex downwards and its ltop open for the overflow of the finer fractubular shaft fixed in relation to the static cone and projecting vertically downwards at the centre thereof, a second tubular shaft embracing the first and movable vertically in relationfthereto, a body attached to the lower `end ofthe second tubular shaft to float submerged in the lower partof the to the third tubular shaft at a level to float partly submerged and to define between itself and the static cone a classifying column of variable cross section, cooperating abutments on the outside of the second tubular shaft and the inside of the third to limit the vertical movement of the' third tubular shaft in relation to the second, a sand chamber below the clean water inlet tocollect the` coarser fraction, and a pump connected to the sand chamber tonremove water with the coarser fraction in suspension.

8. A classifier of the hindered settling type comprising a static cone w'th its apex downwards' 'and its top open for theoveriiow of the finer fraction, a feed inlet at the top for water containing in suspension the material to be classified, a clean water inlet at the lower end 'of the static cone, a tubular shaft fixed in relation to the static cone and projecting vertically downwards at the centre thereof, a second tubular shaft embracing theirst and movable vertically in 4relation thereto, a

body attached to the lower end o-f the second tubular shaft to float submerged in the lower part of the static cone and to define between itself and the static cone a hindered settling column of variabley cross-section, cooperating abutments on theoutside of the first tubular shaft and the inside of the second to limit the vertical movement of the second tubular shaft and the floating body, a

third tubular shaft embracing the second and movabley vertically in relation thereto, a body of annular form fixed to the third tubular shaft at a level to float partly submerged and to denne bey the said annular body, cooperating abutments on static cone and 'to define 'between itself and the vthe second to limit the vertical movement of 'the static cone a hindered settling column of var-able- CI'OSS-BBCMOH, Cooperating abutments on the out-H 70l to collect the c oarser fraction, and a-pump consecond tubular shaftA and the floating body, a

second body located to float partly submerged at a I y variable level in the upper part of thestatic cone .and to define betweenitself and the lstaticcone Va tween itself and the static cone a classifying column 'of variable cross-section, the feedA inlet being arranged to discharge `the material .inside the outside of the secondv tubular shaft and the inside of the third to limit the vertical movement of the third tubular shaft in relation to the second'. a sand chamber below the clean water inlet nected to the said chamber to remove water with the coarser fraction in suspension.

9. A classiiierof the hirrdered settling type comprisinga static cone with its apex downwardsand its top open for the overflow of the finer fr tion, a' tangential feed inlet at the top for water Icontaining in suspension the material to be classied, aclean water inlet volute at the lower end of the static cone having the same direction of swirl as the said feed inlet, a tubular shaft fixed in relationto the static cone and projecting vermerged at a variable level in the upper part of the static cone and to define between itself and the static cone a classifying column of variable cross-section, a sand chamber below the clean water inlet to collect the coarser fraction, a by- C pass pipe between the clean water inlet and the tically downwards at the centre thereof, a secl v ond body located to float partly vsubmerged at a variable level in the upper part of the static cone and to deflnebetween itself and the static cone a classifying column of variable cross-section. vanas in vertical'planes associated with at least one of the floating bodies to keepboth/bodies in slow ro-v tation due to the swirl in the liquid, a sand chamber below the clean water inlet to .icollect the coarser fraction, and a' pumpconnecfed to the sand chamber to remove water with the 'fraction in suspension.

l0. Aclassiiier of thehindered settling type comprising a static cone with its apex downwards and its topl open for the overilowof the nerfraction, a tangential-feed inlet at the top coarser for water containing insuspension the material to be classified, a clean water inlet volute at the lower end of the static cone having the same dlrection of swirl as the said feed inlet, a body lo`- pump, a regulating valve in the bypa$s Pipe. and a second regulating valve between the commencement of the by-pass pipe and the clean water inlet.

- l2. lA classifier as dened in Claim 7 in which the first floating body ls in the form of an upper upright cone and a lower inverted cone with an intermediate trunco-conical portion having its apex downwards and of a smaller vertical angle than the lower inverted cone, and in which the second floating Vbody is in the form of an inner cylinder and an outer cylinder Joined at the top by an upright truncated cone andw at the bottom by an inverted truncated cone, the said body l being mounted on the third4 shaft in such a posicated to float submerged -at 'a variable level inv 'the lower part of the static cone and to define bef tween itself and the static cone a hindered settling column of variable cross-section, a second body located to float partly submerged at a variable level in the upper part of the static cone andto define between itself and the static cone a olassifyingcolumn of variable cross-section, a sand chamber of at least partly conical form below'the y clean water inlet volute to collect the coarser fraction, a pump connected to the apex 'at the bbttom'of the sand chamber` to remove water with the coarser fraction in suspension, a second pump. for removal of water with suspended solids, .a suction pipe for the second pump protruding into the sand chamber; means for moving the inlet v .end'of the said suction pipe to 'varying distances from the axis of the sand chamber, and means for adjusting the quantity of liquid drawn .ofl' by theaecondpump.

ll. A classifier` of the hindered settling type tionthat the body floats with the water level in the static cone on the outer cylindrical surface of the said body in every operation position.

13 A classifier ofthe hindered settling' type comprising a static conewith' its apex downwards and its-top open for the overflow of the finer fraction, a clean water inlet at the lower end of the static cone, a body located to float submerged at a variable level in the lower part of the static cone and to .define between itself and the static cone a hindered settling column of variable cross-section, a second body of annular form located to float partly submerged at a variable level inthe upper part of the static cone and to define between itself andv the static cone a classifyingcolumn oi' variable cross-section, a feed inlet box bounded by inner and vouter cylindrical faces and upper vand lower annular at faces located with its lower end within the upper part oi' the said annular floating body. a tanvVariable aperture in the gentially directed inlet pipe terminating in the upper ilat face for water containing in suspension the material to be classified, discharge holesyof lower fiat face, outlet ports in the' outer cylindrical faceA of the feed box, diverting plates over the ports set at an angle to the cyundriczu face to agree with the swirl due to the tangential inlet pipe, a sand chamber attached to the static cone below the clean water inlet to collect the coarser fraction, and a pump vcomprising a static cone with its apex downi A l wards and its top open for 'the 'overflow of the ilner fraction, 'a feed inlet at the top for waterv l containing in suspension the material to be clas- Y static cone, afbody located to oat vsubmerged at a variable level in the lower part of the static cone t and to define between itself and the static cone a' hindered settling column of-'variable cross-sec- -A siiied, aclean water ilet at the lower end of the connected to the sand chamber' to remove water with the coarselfraction in suspension'.

t 14. A dessiner as dennen in claim 5 includingv also an overload device, in which the overload devicecomprlses a lever with its fulcrum fixed in relation to the static cone, a ring attached to one arm oi' the lever and embracing the fixed tubular shaft, the ring `being normally' at such a level as just to make contact with a member" fast with the second floating body when the latter is at its full load position, and means connected to the other arm of the lever to divert when the ring is raised a portion of the water containing in suspension the material to be classified at some position prior to its entry into the feed inlet.

vJOHN DnGoR'Y BARON Prairies.4 

